Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757641AbbLCMRR (ORCPT ); Thu, 3 Dec 2015 07:17:17 -0500 Received: from foss.arm.com ([217.140.101.70]:48622 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751854AbbLCMRP (ORCPT ); Thu, 3 Dec 2015 07:17:15 -0500 Date: Thu, 3 Dec 2015 12:17:12 +0000 From: Will Deacon To: Daniel Cashman Cc: linux-kernel@vger.kernel.org, linux@arm.linux.org.uk, akpm@linux-foundation.org, keescook@chromium.org, mingo@kernel.org, linux-arm-kernel@lists.infradead.org, corbet@lwn.net, dzickus@redhat.com, ebiederm@xmission.com, xypron.glpk@gmx.de, jpoimboe@redhat.com, kirill.shutemov@linux.intel.com, n-horiguchi@ah.jp.nec.com, aarcange@redhat.com, mgorman@suse.de, tglx@linutronix.de, rientjes@google.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, salyzyn@android.com, jeffv@google.com, nnk@google.com, catalin.marinas@arm.com, hpa@zytor.com, x86@kernel.org, hecmargi@upv.es, bp@suse.de, dcashman@google.com, arnd@arndb.de Subject: Re: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. Message-ID: <20151203121712.GE11337@arm.com> References: <1449000658-11475-1-git-send-email-dcashman@android.com> <1449000658-11475-2-git-send-email-dcashman@android.com> <1449000658-11475-3-git-send-email-dcashman@android.com> <1449000658-11475-4-git-send-email-dcashman@android.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1449000658-11475-4-git-send-email-dcashman@android.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2716 Lines: 71 Hi Daniel, On Tue, Dec 01, 2015 at 12:10:57PM -0800, Daniel Cashman wrote: > From: dcashman > > arm64: arch_mmap_rnd() uses STACK_RND_MASK to generate the > random offset for the mmap base address. This value represents a > compromise between increased ASLR effectiveness and avoiding > address-space fragmentation. Replace it with a Kconfig option, which > is sensibly bounded, so that platform developers may choose where to > place this compromise. Keep default values as new minimums. > > Signed-off-by: Daniel Cashman > --- > arch/arm64/Kconfig | 31 +++++++++++++++++++++++++++++++ > arch/arm64/mm/mmap.c | 8 ++++++-- > 2 files changed, 37 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 871f217..fb57649 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -51,6 +51,8 @@ config ARM64 > select HAVE_ARCH_JUMP_LABEL > select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP && !(ARM64_16K_PAGES && ARM64_VA_BITS_48) > select HAVE_ARCH_KGDB > + select HAVE_ARCH_MMAP_RND_BITS if MMU > + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT You can drop the 'if MMU' bits, since we don't support !MMU on arm64. > select HAVE_ARCH_SECCOMP_FILTER > select HAVE_ARCH_TRACEHOOK > select HAVE_BPF_JIT > @@ -104,6 +106,35 @@ config ARCH_PHYS_ADDR_T_64BIT > config MMU > def_bool y > > +config ARCH_MMAP_RND_BITS_MIN > + default 15 if ARM64_64K_PAGES > + default 17 if ARM64_16K_PAGES > + default 19 Is this correct? We currently have a mask of 0x3ffff, so that's 18 bits. > +config ARCH_MMAP_RND_BITS_MAX > + default 19 if ARM64_VA_BITS=36 > + default 20 if ARM64_64K_PAGES && ARM64_VA_BITS=39 > + default 22 if ARM64_16K_PAGES && ARM64_VA_BITS=39 > + default 24 if ARM64_VA_BITS=39 > + default 23 if ARM64_64K_PAGES && ARM64_VA_BITS=42 > + default 25 if ARM64_16K_PAGES && ARM64_VA_BITS=42 > + default 27 if ARM64_VA_BITS=42 > + default 30 if ARM64_VA_BITS=47 > + default 29 if ARM64_64K_PAGES && ARM64_VA_BITS=48 > + default 31 if ARM64_16K_PAGES && ARM64_VA_BITS=48 > + default 33 if ARM64_VA_BITS=48 > + default 15 if ARM64_64K_PAGES > + default 17 if ARM64_16K_PAGES > + default 19 Could you add a comment above this with the formula (VA_BITS - PAGE_SHIFT - 3), please, so that we can update this easily in the future if we need to? Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/